tests: Trigger dir heal by lookup

Heal full in v2 needs some improvements which Ravi
is working on. Fixed the script to heal based on lookup
from mount until then.

Change-Id: I7b5f8a294019d9f8cfc9c2346d7997f31b4c3d7c
BUG: 1092850
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/8178
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Ravishankar N <ravishankar@redhat.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>